The present invention relates to a joystick having a hand-grip, which is mounted with two degrees of freedom in a mounting in a housing and which may be deflected in different directions out of an initial position, the grip being biased by a spring mechanism back towards its initial position and the different positions of the grip being sensed by sensor apparatus which outputs a signal which is used to control machine and/or vehicle functions.
As regards the mounting, use may be made of a ball-and-socket joint or a cardan joint. A cardan joint comprises three joint portions, which are pivotally connected by means of guides. These guides consist of a large number of individual parts. Moreover, the effort required for assembly is great. Ball-and-socket joints have three degrees of freedom. However, in the case of joysticks, rotation about the grip axis is not required. On that account, such rotation is prevented by a pin which is fastened to the socket and engages in a vertical groove in the ball. This arrangement, however, is susceptible to wear and is only capable of bearing light stresses. The problem on which the present invention is based is to provide a joystick which overcomes or mitigates the aforementioned disadvantages. In particular, it is desirable that the joystick should be economic to manufacture and easy to install.
In regard to a joystick having a grip, which is mounted with two degrees of freedom in a mounting in a housing and which may be deflected in different directions out of an initial position, the grip being biased by a spring mechanism back towards its initial position and in which the different positions of the grip are sensed by sensor apparatus which outputs a signal which is used to control machine and/or vehicle functions, it is proposed that on the underside of a housing cover which has its upper side directed towards the grip, there should be pivotally mounted a cardan joint centre portion on whose underside there is pivotally mounted a cardan joint inner portion, whose underside is provided with spherical segments, which are mounted in complementary bearing cup-portions provided on a receiving support. In regard to the device according to the invention, there may be employed a cardan joint in which the bottom half is cut away. Because of this, the joint can easily be assembled by engaging the parts together. The receiving support prevents the elements of the cardan joint from coming apart.
A particular embodiment of the invention is characterised in that on the side of the cardan joint inner portion which is directed away from the grip, there is provided a magnet whose movement is recorded by a sensor carried by a printed-circuit board which is mounted in the housing. By this means it is readily guaranteed that the deflection of the grip will be accurately sensed. In addition, the number of individual parts of the joystick is kept small.
Another particular embodiment of the invention is characterised in that the grip comprises a grip tube having a stop for a spring, which is biased against a plate which engages on the housing cover. The spring ensures that after the grip is deflected, it is restored to its initial position. The joint portions are pulled upwards by the force of the spring.
In regard to the joystick described at the beginning, the position of the joystick is sensed by sensors which provide an output in the form of an electrical signal. This signal is used to control machine and vehicle functions. In most cases, several switches are disposed in the grip of the joystick. The cables for these switches may possibly be led through a corresponding recess in the joint. If the joystick is used in agricultural and construction machines, it must be capable of withstanding high loadings. The mounting of the joystick must therefore be dimensioned correspondingly sturdily. The provision of the recess for the cables which are led through the mounting also leads to the dimensions of the joystick being increased. In conventional joysticks, the sensors are attached outside the mounting. When using Hall sensors, there is fastened to the grip tube a magnet which is disposed in proximity to a sensor which is fastened to the housing. Depending on the position of the grip and of the magnet, the voltage at the sensor varies. The attachment of magnet and sensor outside the mounting leads to a relatively large spacing between magnet and sensor. This has the result that very large magnets must be used in order to guarantee effective functioning of the joystick.
A further problem which the invention seeks to solve is therefore that of reducing the dimensions of the housing of the joystick. In particular, it is desirable that the spacing between magnet and sensor should to be reduced.
In regard to a joystick having a grip, which is mounted with two degrees of freedom in a mounting in a housing and which may be deflected in different directions out of an initial position, the grip being moved by a spring mechanism back into its initial position and the different positions of the grip being sensed by a sensor apparatus which outputs a signal which is used to control machine and/or vehicle functions, it is proposed in a preferred embodiment of the invention, that the sensor apparatus should be arranged inside the mounting. This has the advantage that when using Hall sensors, the spacing between magnet and sensor is reduced. Moreover, the susceptibility to interference as a result of electromagnetic influences from outside the housing of the joystick is reduced.
One particular embodiment of the invention is characterised in that the mounting is provided by a cardan joint having a substantially annular cardan joint centre portion which is mounted in the housing, and a cardan joint inner portion which is mounted by means of a rotary guide in the cardan joint centre portion and is fork-shaped. As a result of the fork-shaped construction of the cardan joint inner portion, space for a sensor apparatus is provided in the cardan joint.
Another particular embodiment of the invention is characterised in that the rotary guide comprises bearing pins which are attached to the cardan joint inner portion and are guided in slide bushes which are fastened in the cardan joint centre portion. The guiding of the bearing pins in the slide bushes guarantees smooth working and virtually wear-free functioning of the joystick.
Another particular embodiment of the invention is characterised in that on the cardan joint inner portion, there is mounted a ring magnet which cooperates with sensors which are attached to a printed-circuit board, which is fastened to the housing, underneath the ring magnet, with the aid of a support. In the event of a deflection of the grip, the ring magnet mounted on the cardan joint inner portion executes a movement corresponding to the deflection of the grip. The movement of the ring magnet is sensed with the aid of the sensors arranged in the vicinity.
Another particular embodiment of the invention is characterised in that the printed-circuit board cooperates with an electronic analysis circuit which is accommodated in the housing. Damage to individual elements of the sensor apparatus on account of improper operation or the effect of dirt is reliably prevented by the arrangement of the complete sensor apparatus inside the housing of the joystick.
Another particular embodiment is characterised in that the grip comprises a grip tube which is formed on the cardan joint inner portion. Because of this, it is achieved that even very great forces may be applied to the grip without damage occurring.
Another particular embodiment of the invention is characterised in that on the grip, there is mounted at least one switch which serves to control machine and/or vehicle functions and is connected by means of at least one cable, which is led through the grip tube, the ring magnet and the support, to the electronic analysis circuit. The guiding of the cable through the ring magnet guarantees reliable functioning of the joystick in every desired configuration.
Another particular embodiment of the invention is characterised in that the deflection region of the joystick comprises a first region, in which the restoring force of the grip increases only comparatively slightly, and a second so-called dwell-pressure region in which the grip, having passed a pressure-point, can move a little further, and in that at least one arcuately shaped leaf spring is fastened to the grip tube with the aid of a mounting. In one known device, a spring-mounted locking ram is fastened to each axis. This locking ram is pressed by a spring against a ramp fastened to the housing. The behaviour of the grip during return to its position can be influenced by the shape of the ramp. The restoring force of the grip changes as a function of the angle of the ramp in relation to the direction of movement of the ram. This conventional solution requires a separation of the axes of movement of the grip. Moreover, it is necessary to provide space for the ramp in the vicinity of the axes of movement. The assembly dimensions of the joystick are increased because of this. These disadvantages are avoided in one particular embodiment of the invention, by means of an arcuately shaped leaf spring which may be attached to the grip tube. Moreover, the invention makes it possible to manage with fewer individual parts than is the case in known devices.
A further particular embodiment of the invention is characterised in that in the mounting, a recess is provided for the purpose of receiving the deformed leaf spring. The movement of the spring may then be limited by the size of the recess. Deformation of the spring in the reverse direction is prevented by this limitation of the movement of the spring.
Another particular embodiment of the invention is characterised in that the deflection region of the joystick comprises a first region, in which the restoring force of the grip increases only comparatively slightly, and a second so-called dwell-pressure region in which the grip, having passed a pressure point, can move a little further, and in that on the grip, there is displaceably mounted at least one spring-biased ram which cooperates with a detent contour provided at the edge of a connecting member, which detent contour limits the deflection of the grip.
The geometric configuration of the detent contour may be chosen so as to determine whether the grip will engage in the end position or will spring back.
Other advantages, features and details of the invention are disclosed in the following description, given with reference to the drawings, in which different embodiments of the invention are shown, by way of example only. In this connection, the features mentioned in the description and in the appended claims may be relevant to the invention either individually or in combination. In the drawings: